The integrity of the supply chain of fruits and vegetables is important to public health and well-being. With expanding global trade, the issue of unsafe imported foods has become more acute and fresh produce remains a top food category for both number of foodborne illnesses and outbreaks. Prevalence of pathogens in the production environment, risks during harvest, cross-contamination in handling, and temperature fluctuations all suggest an opportunity for tracing the cumulative effects of these events on microorganisms on products from farm to retail. The goal was to demonstrate and describe microbial dynamics in the postharvest supply chain of fresh tomatoes. An observational study was conducted on tomatoes sampled from four locations of the postharvest supply chain from Mexico to USA and analyzed individually for microbial populations: aerobic mesophiles (APC), total coliforms (TC), generic Escherichia coli (EC), and yeasts/molds (YM). APC differed (p